What Is the Spur Gear Hertz Contact Stress & Surface Fatigue Pitting Calculator?
Gear tooth failure occurs either through root bending fracture or contact surface fatigue pitting caused by cyclic Hertzian compressive stresses between meshing involute flanks.
Surface fatigue produces microscopic micro-cracks that flake into pits, degrading tooth accuracy and causing noise and eventual catastrophic tooth surface spalling.
This calculator applies the AGMA contact stress equation, accounting for tangential load, pinion pitch diameter, elasticity coefficient Z_E, and involute curvature.
How Does the Spur Gear Hertz Contact Stress & Surface Fatigue Pitting Calculator Work?
The calculation evaluates user-provided measurements using recognized domain equations, converts between measurement units, and adjusts for real-world efficiency factors.
Spur Gear Hertz Contact Stress & Surface Fatigue Pitting Calculator Formula & Variables
The core mathematical equation utilized by this calculator is expressed as:
AGMA Hertzian contact compressive stress formula between cylindrical involute tooth profiles.
How to Use the Spur Gear Hertz Contact Stress & Surface Fatigue Pitting Calculator
- Enter your primary measurements in the input fields above.
- Select your preferred units (e.g. metric or imperial) if applicable.
- Review or adjust operational assumptions such as field efficiency.
- Click Calculate to instantly generate the full results breakdown and visual chart.
- Use the Reset button at any time to clear the form and test a new scenario.
Step-by-Step Example Calculation
Pinion-Gear Drive (d1 = 50mm, d2 = 150mm, Wt = 2200N, b = 25mm)
Input Values:
Understanding Your Result
Your calculated result represents the realistic operational capacity or baseline output under the specified conditions. Comparing theoretical and effective outputs reveals the direct impact of turns, overlap, and practical downtime.
Factors That Affect the Result
Field terrain, operator experience, equipment maintenance, overlap margin, and weather conditions can significantly influence real-world output.
When Should You Use This Calculator?
Use this calculator whenever you need quick, verified estimates for job planning, budgeting, equipment sizing, or project timelines.
Assumptions & Limitations
- Geometry Factor: I = [cos φ · sin φ / 2] · [m_G / (m_G + 1)], where m_G = d₂ / d₁.
- AGMA Contact Stress: σ_H = Z_E · √[ W_t / (b · d₁ · I) ] (MPa).
- Allowable Contact Stress: Typically 1000 - 1500 MPa for case-hardened alloy steels.
Frequently Asked Questions
Calculation Accuracy & Reference Note
This calculator implements verified, deterministic mathematical equations based on published standards. Results should be treated as professional engineering estimates; always verify critical operations with local equipment manuals and site inspections.